[ocaml-platform] Changes to my previous proposal for namespaces

[Leo White]

> Can the case of both Core and Async (and opening both of their pervasives modules) be handled here?  This seems to me
> to be of fundamental importance.  If that's missing, then I misunderstood the proposal.

Yes that is fine. It just means that if you made a new namespace by
merging the Core namespace with the Async namespace then the Pervasives
module of one would shadow the Pervasives module of the other.